Methods and apparatus for a capacitive sensor

ABSTRACT

Various embodiments of the present technology may comprise methods and apparatus for increased sensitivity of a capacitive proximity sensor. The method and apparatus may comprise a sensing element with a plurality of multi-operation electrodes configured to operate as one of a transmission electrode and a reception electrode to increase the strength of the sensing field. Each of the multi-operation electrodes may be selectively operated by a detection circuit to couple one multi-operation electrode to an amplifier and each remaining multi-operation electrode to a voltage source.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of prior application Ser. No.15/283,872, filed Oct. 3, 2016, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/246,238, filed on Oct. 26,2015, and incorporates the disclosure of the application in its entiretyby reference.

BACKGROUND OF THE TECHNOLOGY

Capacitive sensors operate by detecting changes in the capacitanceformed between a transmission electrode and a sense electrode. A sensingcircuit can recognize an object and determine the location, pressure,direction, speed and acceleration of the object as it is approachesand/or moves across the touch surface.

Electronic devices with touch sensing surfaces may utilize variouscapacitive sensing devices to allow a user to make selections and moveobjects by moving their finger (or stylus) relative to a capacitivesensing element. Mutual capacitance touch sensors not only have theability to detect touch events on the sensing surface, but also have theability to detect proximity events, in which an object is not touchingthe sensing surface, but is in close proximity to the sensing surface.The mutual capacitive touch sensor operates by measuring the capacitanceof the capacitive sense element, and looking for a change in capacitanceindicating a touch or presence of a conductive object. When theconductive object (e.g., a finger, hand, foot, or other object) comesinto contact or close proximity with a capacitive sense element, thecapacitance changes and the conductive object is detected. An electricalcircuit may be utilized to measure the change in capacitance of thecapacitive touch sense element, and the electrical circuit may convertthe measured capacitance of the capacitive sense element into a digitalvalue.

The ability of the mutual capacitance touch sensors to detect objects inclose proximity to the sensing surface is limited by the size andoperating specifications of the electronic device. In an effort toreduce the size of electronic devices, the size of the operationalcomponents, such as microprocessor chips, printed circuit boards,displays, memory chips, hard drives, batteries, interconnectivitycircuitry, indicators, input mechanisms, and the like, are also reduced.There is, however, a desire to maintain operational specifications, suchas operating power specifications, while increasing the functionality ofthe touch sensor.

Capacitive sensors may also be utilized to measure a volume and/or alevel of some material, such as fluids, within a container. Capacitivesensors utilized in such applications may provide a more accuratemeasurement and may be more reliable than conventional indicators.

SUMMARY OF THE INVENTION

Various embodiments of the present technology may comprise methods andapparatus for increased sensitivity of a capacitive proximity sensor.The method and apparatus may comprise a sensing element with a pluralityof multi-operation electrodes configured to operate as one of atransmission electrode and a reception electrode to increase thestrength of the sensing field. Each of the multi-operation electrodesmay be selectively operated by a detection circuit to couple onemulti-operation electrode to an amplifier and each remainingmulti-operation electrode to a voltage source.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present technology may be derivedby referring to the detailed description when considered in connectionwith the following illustrative figures. In the following figures, likereference numbers refer to similar elements and steps throughout thefigures.

FIGS. 1A and 1B representatively illustrate a capacitive proximitysensor in accordance with a first exemplary embodiment of the presenttechnology;

FIG. 2 graphically illustrates a relationship between distance from asensing surface and capacitance of a capacitive proximity sensor inaccordance with an exemplary embodiment of the present technology;

FIG. 3 representatively illustrates a capacitive proximity sensor inaccordance with an exemplary embodiment of the present technology;

FIG. 4 graphically illustrates a relationship between distance from asensing surface and output voltage of a capacitive proximity sensor inaccordance with an exemplary embodiment of the present technology;

FIG. 5 is an equivalent circuit diagram of a capacitive proximity sensorin accordance with an exemplary embodiment of the present technology;

FIG. 6 is an equivalent circuit diagram of a capacitive proximity sensorin accordance with an exemplary embodiment of the present technology;

FIG. 7 is an equivalent circuit diagram of a capacitive proximity sensorin accordance with an exemplary embodiment of the present technology;

FIGS. 8 representatively illustrates a capacitive proximity sensor inaccordance with an exemplary embodiment of the present technology;

FIG. 9 is an equivalent circuit diagram of a capacitive proximity sensorin accordance with an exemplary embodiment of the present technology;

FIG. 10 is a partial circuit diagram of a capacitive proximity sensor inaccordance with an exemplary embodiment of the present technology;

FIGS. 11A-C representatively illustrates operation of a capacitiveproximity sensor in accordance with an exemplary embodiment of thepresent technology;

FIGS. 12A-C representatively illustrate a multi-plane capacitiveproximity sensor in accordance with an exemplary embodiment of thepresent technology;

FIG. 13 representatively illustrates a multi-plane capacitive sensor inaccordance with an exemplary embodiment of the present technology;

FIGS. 14A-B representatively illustrate a capacitive sensor inaccordance with an exemplary embodiment of the present technology;

FIG. 15 representatively illustrates a 3-dimensional capacitive sensorin accordance with an exemplary embodiment of the present technology;

FIG. 16 representatively illustrates a 3-dimensional capacitive sensorin accordance with an exemplary embodiment of the present technology;

FIG. 17 representatively illustrates a 3-dimensional capacitive sensorin accordance with an exemplary embodiment of the present technology;and

FIG. 18 representatively illustrates a 3-dimensional capacitive sensorin accordance with an exemplary embodiment of the present technology.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present technology may be described in terms of functional blockcomponents and circuit diagrams. Such functional blocks and circuitdiagrams may be realized by any number of components configured toperform the specified functions and achieve the various results. Forexample, the present technology may employ various types of capacitors,amplifiers, power sources, and the like, which may carry out a varietyof functions. The methods and apparatus for a capacitive proximitysensor according to various aspects of the present technology mayoperate in conjunction with any electronic device and/or device inputapplication, such as a cellular phone, an audio device, a gaming device,a television, a personal computer, and the like.

Referring to FIGS. 1A-B, 3, 4, and 5, in various embodiments of thepresent technology, a capacitive sensor 100 may detect an object bymeasuring a change in a capacitance and/or an output voltage (Vout) ofthe sensor 100. In various embodiments, the capacitive sensor 100 maycomprise a sensing element 105 and operational circuitry that operate inconjunction to create a sensing field 125 and measure changes in thesensing field 125.

The capacitive sensor 100 may generate the sensing field 125, such as anelectric field, at a surface 310 of the sensing element 105. In variousembodiments, the capacitive sensor 100 may operate as a proximity sensorto detect an object within the sensing field 125. The sensing field 125may form in a region between the surface 310 of the sensing element 105and a maximum detection distance 305, where the sensing element 105 maydetect an object 120, such as a human fingertip, a pen point or thelike, when it enters the sensing field 125. As such, the object 120 maynot need to physically touch the sensing element 105 to effect a changein the capacitance.

In various embodiments, the capacitive sensor 100 detect the object 120by measuring and/or detecting changes in a resting capacitance and theoutput voltage of the sensing element 105 as a result of the object 120entering the sensing field 125. In general, and referring to FIGS. 1B,2, and 4, as the object 120 approaches, such as when a person's fingergets close to the sensing element 105 (decreasing a distance 315, FIG.3), some of the sensing field 125 is absorbed by the object 120,decreasing the amount of energy detected by the sensing element 105 andreducing the capacitance. As the object 120 gets closer to the surface310 of the sensing element 105, more of the sensing field 125 isabsorbed by the object 120 and the capacitance may continue to decrease,causing Vout to increase. As Vout changes according to the amount ofenergy detected by the sensing element 105, it may be possible toquantify or otherwise estimate the distance 315 between the object 120and the surface 310 of the sensing element 105.

In various embodiments, the capacitive sensor 100 may detect when Voutreaches and/or exceeds a predetermined threshold. For example, andreferring to FIG. 4, the capacitive sensor 100 may respond to a firstpredetermined threshold 405 and respond again to a second predeterminedthreshold 410. The capacitive sensor 100 may transmit a signal to acontroller (not shown) when Vout reaches one of the predeterminedthresholds to trigger an output circuit (not shown) to switch statesbetween ON and OFF, which may indicate some input selection of anelectronic device, such as a cellular phone.

The sensing element 105 may produce the sensing field 125 and respond toobjects entering and/or within the sensing field 125. The sensingelement 105 may comprise any suitable device or system responsive to thesensing field 125. The sensing element 105 may comprise input devices,such as buttons, switches, dials, sliders, keys or keypads, navigationpads, touch pads, touch screens, and the like. The sensing element 105may be formed within an insulation substrate (not shown), such as a PCBsubstrate in an electronic device, such as a cellular phone, personalcomputer, and the like. For example, and referring to FIGS. 3, 8, 12,and 13, in various embodiments, the sensing element 105 may comprise aplurality of electrodes 135 suitably configured to form the sensingfield 125. In various embodiments, at least one electrode 135 maycomprise a drive electrode 110 (i.e., a transmission electrode) and atleast one electrode 135 may comprise a reception electrode 115, whereinthe transmission electrode 110 and the reception electrode 115 form asensing capacitor Cs, having a capacitance value CA1. The electrodes 135may have any physical arrangement and may be formed of any shape or sizefor a particular application.

Referring to FIG. 3, in an exemplary embodiment, the sensing element 105comprises a first electrode 135 a and a second electrode 135 b, whereinthe first and second electrodes 135 a, 135 b may be coplanar. In thepresent embodiment, the first electrode 135 a may comprise thetransmission electrode 110 and the second electrode 135 b may comprisethe reception electrode 115, wherein the first and second electrodes 135a, 135 b together form the sensing capacitor Cs. For example, thesensing element 105 may comprise a total surface area A, wherein thefirst electrode 135 a may comprise a first surface area A1 definedgenerally by the dimensions of the surface 310 of the sensing element105. The second electrode 135 b may comprise a second surface area A2that is surrounded by the first electrode 135 a and separated by adielectric 130, wherein the dielectric surrounds the second electrode135 b. The reception electrode 115 may be coupled to a voltage source510 (FIG. 5).

Referring to FIG. 8, in an alternative embodiment, the sensing element105 may comprise a plurality of electrodes suitably configured toproduce the sensing field 125. In the present embodiment, the sensingelement 105 may comprise the electrode 135 configured to operate as thetransmission electrode 110 (i.e., a single-operation electrode). Thesensing element 105 further comprises a plurality of multi-operationelectrodes 140 suitably configured to operate as the transmissionelectrode 110 and the reception electrode 115. For example, only onemulti-operation electrode 140 may operate as the reception electrode115, while the remaining multi-operation electrodes 140 operate astransmission electrodes 110. As such, the multi-operation electrode 140operating as the reception electrode 115 and the remaining electrodesoperating as the transmission electrodes 110, form the sensing capacitorCs.

The multi-operation electrodes may be coplanar with the electrode 135wherein the plurality of multi-operation electrodes 140 are nestedinside and surrounded by the electrode 135. The dielectric 130 maysurround each multi-operation electrode 140 to insulate them from theelectrode 135. In an exemplary embodiment, the multi-operationelectrodes 140 are aligned along one direction and substantiallyequidistant from one another. In alternative embodiments, themulti-operation electrodes 140 may be aligned vertically andhorizontally to form an array.

The sensing field 125 may exhibit increased sensitivity above thesurface 310 of the sensing element 105, as well as in a lateraldirection from the multi-operation electrode 140 operating as thereception electrode 115. In the present embodiment, the electrode 135,may comprise a third surface area A3, and each multi-operation electrode140 may comprise a fourth surface area A4, wherein the fourth surfaceareas A4 are equal.

Referring to FIGS. 9 and 12 through 18, in an alternative embodiment,the capacitive sensor 100 may be configured to detect volume, a positionof an object in a 3-dimensional space, the presence or absence of anobject in the 3-dimensional space, and other characteristics of the3-dimensional space. For example, the sensing element 105 of thecapacitive sensor 100 may be arranged on multiple planes to form asensing region in the space created by the planes. Each plane may besuitably configured to operate as the transmission electrode 110 or thereception electrode 115 according to a desired function or application.

Referring specifically to FIGS. 12A-C, the sensing element 105 maycomprise three surfaces 310 arranged along a first plane 1205 a, asecond plane 1205 b, and a third plane 1205 c. The first plane 1205 aand the second plane 1205 b may be positioned substantially parallel toeach other and the third plane 1205 c may be positioned orthogonallybetween the first and second planes 1205 a, 1205 b. Each surface 310 maycomprise two electrodes, wherein one of the electrodes comprises amulti-operation electrode 140 surrounded by a larger electrode 135. Asdescribed above, the multi-operation electrode 140 may operate as thetransmission electrode 110 and/or the reception electrode 115. The twomulti-operation electrodes 140 on the set of parallel planes, forexample the first and second planes 1205 a, 1205 b, may be at leastsubstantially aligned with each other, wherein the first plane 1205 a ispositioned directly across from the second plane 1205 b.

At any given time, only one of the multi-operation electrodes 140operates as the reception electrode 115 and the remainingmulti-operation electrodes 140 operate as the transmission electrodes110. As such, the sensing capacitor Cs is formed between themulti-operation electrode 140 operating as the reception electrode 115and the remaining electrodes operating as the transmission electrodes110.

The sensing element 105 may form a plurality of sensing fields 125 basedon the operation of the multi-operation electrodes 140 to create aregion 1230 with higher sensitivity. For example, the region 1230 ofhigher sensitivity may comprise a subspace proximate to themulti-operation electrode 140 that is operating as the receptionelectrode 115.

In a third embodiment, and referring to FIG. 13, the sensing element 105may be arranged along parallel planes to measure the capacitance betweenthe two planes. For example, the sensing element 105 may comprise afirst plane 1300 a spaced a predetermined distance from a second plane1300 b. The sensing element 105 may further be configured to measure thecapacitance between more than two planes by comprising a third plane1300 c spaced a second predetermined distance from the second plane 1300b. Each plane may be configured to operate as the transmission electrode110 and/or or the reception electrode 115 (i.e., the multi-operationelectrode 140). In various embodiments, each plane 1300 may also operateas a high impedance electrode. According to the present embodiment, eachplane 1300 may have substantially equal areas and the electrodes 140 maybe aligned.

In yet another alternative embodiment of the capacitive sensor 100, andreferring to FIGS. 14A-B, the sensing element 105 may be arranged onmultiple planes of a 3-dimensional container 1400. For example, two ormore sides of the container 1400 comprise the multi-operation electrode140 to form the sensing field 125, wherein a first side 1430 operates asthe reception electrode 115 and a second side 1435 operates as thetransmission electrode 110. Each multi-operation electrode 140 may beconfigured operate as the reception electrode 115 and the transmissionelectrode 110, as described above.

According to various embodiments, operation of the multi-operationelectrodes 140 may be sequenced, wherein at any given time, only onemulti-operation electrode 140 is operating as the reception electrode115 and one electrode 140 is operating as the transmission electrode110. For example, as shown in FIG. 14A, the multi-operation electrodes140 may be arranged on opposing sides of the container 1400 to create ahorizontal sensing field 125 and to form the sensing capacitor Cs.Alternatively, and as shown in FIG. 14B, the transmission electrode 110and the reception electrode 115 may be arranged on non-parallel sides ofthe container 1400 to create a curved sensing field 125 and to form thesensing capacitor Cs.

The container 1400 may have predetermined dimensions comprising a height1405, a width 1415, and a length 1420. As such, the container 1400 mayhave a maximum volume, equal to a product of the height 1405, the width1415, and the length 1420 (i.e. volume=height×width×length). Thecontainer 1400 may be filled with a material 1425, such as a liquid witha predetermined dielectric constant, to a level 1410. The volume of thematerial 1425 may then be computed based on the container dimensions,capacitance data, and dielectric constant.

The particular arrangement of the sensing element 105 may be adaptedaccording to a desired function or application. For example, andreferring to FIG. 15, the sensing element 105 may comprisemulti-operation electrodes 140 formed on more than three planes. Inanother arrangement, referring to FIGS. 16 and 18 the sensing element105 may comprise two parallel electrodes 140 spaced a predetermineddistance apart and able to accommodate one or more objects to be placebetween the electrodes 140. In yet another arrangement, referring toFIG. 17, the electrodes 140 may be disposed in a non-parallel positionfrom each other.

Referring to FIGS. 5, 6, 7, 9 the capacitive sensor 105 may comprise adetection circuit 500 coupled to the sensing element 105 to detectchanges in the capacitance of the sensing capacitor Cs. The detectioncircuit 500 may comprise any suitable system or method for sensingchanges in capacitance.

The detection circuit 500 may be configured to have a preset internalcapacitance or a variable internal capacitance. For example, in oneembodiment, the detection circuit may comprise a first internal variablecapacitor Cint1 with an adjustable capacitance CAint1 and a secondinternal variable capacitor Cint2 with an adjustable capacitance CAint2.As such, the detection circuit 500 will have a potential internalmaximum capacitance value CAmax defined as the capacitance value whenthe first and second internal variable capacitors Cint1, Cint2 areadjusted to their maximum values. Similarly, the detection circuit willhave a potential minimum capacitance value CAmin defined as thecapacitance value when the first and second internal variable capacitorsCint1, Cint2 are adjusted to their minimum values. In general, a totalinternal IC capacitance CAint_total may be defined as the capacitance ofthe first internal capacitor CAint1_(—) plus the capacitance of thesecond internal capacitor CAint2 (i.e., CAint_total=CAint1+CAint2).

The first internal variable capacitor Cint1 may be electricallyconnected to a voltage source, for example an inverted driving voltagepulse Vdry_bar (by using an inverter 515 to invert the voltage source510) and the inverting input terminal (−) of the differential amplifier505. The second internal variable capacitor Cint2 may be electricallyconnected to the inverted driving voltage pulse Vdrv_bar and thenon-inverting input terminal (+) of the differential amplifier 505.

A surface area of the sensing element 105 may be increased, therebyincreasing the sensitivity of the sensing element 105 by increasing thestrength of the sensing field 125, and increasing the maximum distance305 at which the capacitive sensor 100 may detect an object approachingthe sensing element 105. In various embodiments, the detection circuit500 may accommodate multiple sensing capacitors Cs. In variousembodiments, the capacitive sensor 100 may be able to accommodate asensing element 105 with a capacitance which is larger than the internalcapacitance of the IC.

In general, a ratio of the sensing capacitance CA1 to the first internalvariable capacitance CAint1 is equal to the ratio of the referencecapacitance CAref to the second internal variable capacitance CAint2(i.e., CA1:CAint1=CAref:CAint2). Therefore, a maximum detectioncapacitance Cdet_max, which is defined as the sum of the maximumcapacitance values of the first and second internal capacitors Cint1,Cint2, is limited by the maximum capacitance values of the first andsecond internal capacitors Cint1, Cint2. In some cases, the capacitanceCA1 of the sensing capacitor Cs may exceed the maximum capacitance ofthe first internal variable capacitor Cint1 and the IC will not be ableto accurately detect the capacitance CA1 of the sensing capacitor Cs.

The detection capabilities of the IC may be improved by couplingadditional external (outside of the IC) capacitors coupled to the firstand second variable capacitors Cint1, Cint2. In this case, thecapacitive sensor 100 will have an effective detection capacitanceCdet_eff, wherein the effective detection capacitance Cdet_eff has amaximum value equal to the capacitance of the additional externalcapacitors CAext1, CAext2 plus the potential internal maximumcapacitance of the first and second variable capacitors CAmax. Byincreasing the effective detection capacitance Cdet_eff of thecapacitive sensor 100, the surface area A of the sensing element 105 maybe increased while maintaining the internal capacitance of the IC. Sincecapacitance and area are proportional, increasing the surface area A ofthe sensing element 105 increases the capacitance of the sensingcapacitor Cs, and in turn increases the maximum distance 305 of thesensing field 125.

Referring to FIG. 5, in an exemplary embodiment, the capacitive sensor100 may comprise additional external capacitors to improve the detectioncapability of the capacitive sensor 100. In the present embodiment, thecapacitive sensor 100 comprises the sensing capacitor Cs, the referencecapacitor Cref, a first external capacitor Cext1 with a capacitanceCAext1, and a second external capacitor Cext2 with a capacitance CAext2.As discussed above, the first and second external capacitors Cext1,Cext2 are formed outside of the IC.

In an exemplary embodiment, the first external capacitor Cext1 iscoupled in parallel with the first internal variable capacitor Cint1,and the second external capacitor Cext2 is coupled in parallel with thesecond internal variable capacitor Cint2. Since capacitors coupled inparallel are summed, the total capacitance for each pair is thecapacitance of the external capacitor plus the capacitance of theinternal capacitor.

The sensing capacitor Cs may be electrically connected in series withthe first external capacitor Cext1 and the first internal variablecapacitor Cint1, at a first node N1. The first node N1 may be coupled toan inverting input terminal (−) of a differential amplifier 505. Theinverting input terminal (−) of the differential amplifier 505 mayreceive a signal comprising first capacitance data.

The reference capacitor Cref may be electrically connected in serieswith the second external capacitor Cext2 and the second internalvariable capacitor Cint2 at a second node N2. The second node N2 may becoupled to a non-inverting input terminal (+) of the differentialamplifier 505. The non-inverting input terminal (+) of the differentialamplifier 505 may receive a signal comprising second capacitance data.

The detection circuit 500 may further comprise a first feedbackcapacitance and a second feedback capacitor Cf2. The first feedbackcapacitor Cf1 may be electrically connected between a first outputterminal (−) and the non-inverting input terminal (+) of thedifferential amplifier 505, and the second feedback capacitor Cf2 may beelectrically connected between a second output terminal (+) and theinverting input terminal (−) of the differential amplifier 505. Thefirst and second feedback capacitors Cf1, Cf2 may have the samecapacitance.

In various embodiments, the detection circuit 500 may provide an outputvoltage Vout that corresponds to a difference between the firstcapacitance data and the second capacitance data. The output voltageVout may be defined as the difference between an output voltage Vom fromthe inverting output terminal (−) of the differential amplifier 505 andan output voltage Vop from the non-inverting output terminal (+) of thedifferential amplifier 505 (Vout=Vop−Vom).

Referring to FIG. 6, in an alternative embodiment, the detection circuit500 may be modified to accommodate a plurality of sensing capacitors Cs.In various embodiments, the detection circuit 500 comprises a firstmultiplexer (MUX) 600 coupled to a control unit 605. Various inputsignals of the first MUX 600 may be selectively activated by the controlunit 605, wherein the selected input signal is transmitted to thedifferential amplifier 505

The first MUX 600 may be electrically connected to a plurality ofsensing capacitors Cs, as well as the first external capacitor Cint1. Assuch, the capacitance data transmitted to the differential amplifier 505may comprise any combination of the capacitance of any sensing capacitorCs and the first external capacitor Cext1.

Referring to FIG. 7, in yet another alternative embodiment, thedetection circuit 500 may be modified to accommodate grouped sensingcapacitors Cs. In the present embodiment, the capacitive sensor 100comprises a plurality of sensing capacitors Cs:Cs_(N), a first referencecapacitor Cref1, a second reference capacitor Cref2, first and secondexternal capacitors Cext1, Cext2, a third external capacitor Cext3, anda fourth external capacitor Cext4.

In the present embodiment, the detection circuit 500 may comprise thefirst MUX 600, wherein the first MUX 600 is coupled to the plurality ofsensing capacitors Cs:Cs_(N) and the first and second externalcapacitors Cext1, Cext2. In the present embodiment, the detectioncircuit 500 may further comprise a second MUX 700, wherein the secondMUX 700 is coupled to the first and second reference capacitors Cref1,Cref2 and the third and fourth external capacitors Cext3, Cext4.

In various embodiments, the first and second MUX 600, 700 may receivecontrol signals from the control unit 605 to selectively transmit one ormore input signals to the differential amplifier 505. In the presentembodiment, the first MUX 600 may selectively couple a group of sensingcapacitors Cs to the first external capacitor Cext1 and/or the secondexternal capacitor Cext2. For example, if there are eight (8) sensingcapacitors Cs (i.e., capacitors Cs₁:Cs₈) with capacitance valuesCA1:CA8, the sensing capacitors Cs may be split into two groups: a firstgroup comprising capacitors Cs₁:Cs₄ and a second group comprisingcapacitors Cs₅:Cs₈. The first group may be coupled with the firstexternal capacitor Cext1, while the second group may be coupled with thefirst and second external capacitors Cext1, Cext2. In alternativeembodiments, the plurality of sensing capacitors Cs may be grouped intothree groups. As such, fifth and sixth external capacitors may be added.

In general, for each group of sensing capacitors (i.e., Cs₁:Cs_(N)), thedetection circuit 500 is capable of detecting a range of sensingcapacitance values, the range comprising a maximum capacitance valueCAmax_sense and a minimum capacitance value CAmin_sense. The maximumcapacitance value CAmax_sense is equal to a maximum capacitance value ofthe first internal variable capacitor CAint1_max plus an externalcapacitance CAext (i.e., CAmax_sense=CAint1_max+CAext). Similarly, theminimum capacitance value CAmin_sense is equal to a minimum capacitancevalue of the first internal variable capacitor CAint1_min plus anexternal capacitance CAext (i.e., CAmin_sense=CAint1_min+CAext). Forexample, if the capacitance CAint1 of the first variable internalcapacitor Cint1 ranges from 0 pF to 8 pF, and there are 16 sensingcapacitors Cs with capacitance values: 5 pF, 6 pF, 7 pF, 8 pF, 9 pF, 10pF, 11 pF, 12 pF, 13 pF, 14 pF, 15 pF, 16 pF, 17 pF, 18 pF, 19 pF, 20pF, and the first external capacitance CAext1 is 5 pF, the detectioncircuit 500 is able to detect capacitance values from 5 pF to 13 pF.Similarly, if the first external capacitance CAint1 is 12 pF, thedetection circuit 500 is able to detect capacitance values from 12 pF to20 pF. The detection circuit 500 can only detect the sensing capacitorswith capacitance values that do not exceed the maximum valueCAmax_sense. If the capacitance value exceeds the range set forth above,then the detection circuit 500 will not activate. As such, variousexternal capacitors coupled as inputs to the first and second MUX may beselected accordingly to increase the maximum capacitance valueCmax_sense.

According to various embodiments of the present technology, theeffective detection capacitance Cdet_eff of the IC is increased byconnecting external capacitors Cint1 and Cint2 in parallel with theinternal variable capacitors Cext1, Cext2, respectively. As such, theeffective detection capacitance Cdet_eff is greater than the totalinternal capacitance Cint_total. This arrangement allows greaterdetection capabilities without increasing the total internal maximumcapacitance Cint_total of the IC. For example, in a conventional sensor,if the first internal variable capacitor Cint1 has a maximum capacitanceof 8 pF and the sensing capacitor Cs has a capacitance of 50 pF, thefirst internal variable capacitor Cint1 is not able to adjust to matchthe sensing capacitor Cs. In various embodiments of the presenttechnology, for example, adding the first external capacitor Cext1 witha capacitance of 45 pF provides an effective detection capacitanceCdet_eff of 50 pF that is capable of detecting the capacitance of thesensing capacitor Cs.

According to various embodiments, the detection circuit 500 operates toensure that the capacitive sensor 100 maintains a particular capacitanceratio to improve the accuracy of the output data. The capacitance ratiois optimized when the ratio of the sensing capacitor Cs to the referencecapacitor Cref is equal to the ratio of the effective internalcapacitance (i.e., [Cs:(Cext1+Cint1)]=[Cref:(Cext2+Cint2)].

Referring to FIGS. 9 and 10, in yet another embodiment, the detectioncircuit 500 may comprise a switching element 900, for example atransistor, to selectively couple the multi-operation electrode 140 toone of various electrical connections.

In an exemplary embodiment, the switching element 900 may selectivelycouple the multi-operation electrode 140 to one of a terminal 915 of thedifferential amplifier 505, the voltage source 510, a high impedanceelement 905, or a ground terminal 910. As such, the multi-operationelectrode 140 may operate as the transmission electrode 110, thereception electrode 115, or a ground electrode or a high impedanceelectrode.

In various embodiments, an analog-to-digital converter (not shown) maybe coupled to the output terminals of the differential amplifier 505 toconvert the signal to a digital value. According to variousapplications, the digital value may be transmitted to a centralprocessing unit (not shown) to activate various operations of anelectronic device, such as a cellular phone. For example, the centralprocessing unit may activate a backlight in the phone, perform aselection function, activate various inputs, and the like.

In operation, the capacitive sensor 100 may be utilized to carry out avariety of detection schemes. For example the capacitive sensor 100 maydetect gestures, for example hand motions, the presence or absence of anobject within the 3-dimensional space, the size or shape of an objectwithin the 3-dimensional space, the volume of a material in a container,and a variety of input selections based on the distance 315 from andmovement across the sensing surface 310.

Referring to FIGS. 8 through 11, the capacitive sensor 100 may operateto detect a swiping motion across the surface of the sensing element105. In the present embodiment, the capacitive sensor 100 comprises aplurality of the multi-operation electrodes 140 arranged next to eachother with the transmission electrode 110 surrounding the plurality ofthe multi-operation electrodes 140, and each multi-operation electrode140 is coupled to a dedicated switching element 900.

As the object 120 enters and interferes with the sensing field 125, themulti-operation electrode 140 receiving the most interference (i.e., anactive electrode) from the object 120 will activate the associatedswitching element 900 to connect to the differential amplifier 505. Inthis case, the multi-operation electrode 140 coupled to the differentialamplifier 505 is operating as the reception electrode 115. The remainingmulti-operation electrodes (i.e., inactive electrodes), may beelectrically coupled, via the switching elements 900, to the voltagesource 510 (rather than the ground terminal 910) and operate astransmission electrodes 110. For example, and referring now to FIGS.11A-C, the sensing element 105 comprises a transmission electrode 110,and a first, second, and third multi-operation electrode 140 a, 140 b,140 c. As the object 120 enters the sensing field 125, the capacitivesensor 100 senses the object 120 near one of the electrodes, in thiscase the first multi-operation electrode 140 a, and couples the secondand third multi-operation electrodes 140 b, 140 c to the voltage source510 (FIG. 9) so that they also operate as transmission electrodes 110.As the object 120 moves laterally, the capacitive sensor 100 senses thatthe object 120 is now closer to a different electrode, in this case thesecond multi-operation electrode 140 b, and couples that electrode tothe differential amplifier terminal 915, wherein the secondmulti-operation electrode 140 b now operates as the reception electrode110, and the first and third multi-operation electrodes 140 a, 140 c arecoupled to the voltage source 510 to operate as the transmissionelectrode 110. As the object 120 moves again in the same lateraldirection, the third multi-operation electrode 140 c operates as thereception electrode 110, while the first and second multi-operationelectrodes 140 a, 140 b are coupled to the voltage source 510 to operateas the transmission electrodes 110.

In general, coupling the inactive electrodes to the voltage source 510,rather than the ground terminal 910, may increase the sensitivity of thecapacitive sensor 100, since connecting to the ground terminal 910 mayredirect the sensing field 125 causing a reduction in the proximitysensitivity and reducing the maximum detection distance 305 (FIG. 3).

In various embodiments, the sensing element 105 may be electricallyconnected to a plurality of channels (not shown) representing multipleinputs to one sensing element 105. For example, as the object 120 entersthe sensing field 125, a first channel may be activated by a firstpredetermined voltage level which may, for example cause a screen of anelectronic device, such as a cell phone, to light up. As the object 120moves closer to the surface 310 of the sensing element 105 and theoutput voltage Vout increases, a second channel may be activated by asecond predetermined voltage level which may cause an activation and/orselection of an input, such as a button, within the electronic device.

Referring to FIGS. 9, 10, 12A-C, and 15, the capacitive sensor 100 mayoperate to detect the position and/or movement of the object within a3-dimensional space, and/or detect the presence or absence of an objectwithin the 3-dimensional space. In the present embodiment, thecapacitive sensor 100 comprises a plurality of multi-operationelectrodes 140 surrounded by the transmission electrode 110 and arrangedon various planes to form a 3-dimensional space, wherein each planecomprises a sensing surface 310. In the present embodiment, thecapacitive sensor 100 further comprises the switching element 900 sothat each multi-operation electrode 140 may operate as a either atransmission electrode 110 or a reception electrode 115 in a similarmanner as described above for a single plane configuration.

In this embodiment, as the object 120 enters the sensing region 1230,the multi-operation electrodes 140 may couple and uncouple to thevoltage source 510 in a sequenced manner. In the present embodiment,only one multi-operation electrode 140 operates as the receptionelectrode 115 at any given time. The detection circuit 500 outputs asignal that corresponds to the distance 315 from the object 120 to thesensing surface 310. The capacitance data from each multi-operationelectrode 140, when it is operating as the reception electrode 110, maybe utilized to determine the coordinates of the object 120 within the3-dimensional space. For example, the capacitive sensor 100 may comprisea processing unit (not shown) coupled to the output of the detectioncircuit 500 to receive and process the data.

Alternatively, the capacitive sensor 100 may detect the presence orabsence of a stationary object based on a predetermined restingcapacitance measured when there are no objects within the sensing field.

In the present embodiment, the capacitive sensor 100 may exhibitincreases sensitivity and a larger sensing region 1230 than conventionalsensors by coupling the multi-operation electrodes 140 to either thevoltage source 510 or the differential amplifier terminal 915, ratherthan the ground terminal 910, since connecting to the ground terminal910 may redirect the sensing field 125, which may create a region wherethe object 120 is non-detectable.

Referring again to FIGS. 9, 10, 13, 14, 16, 17, and 18, the capacitivesensor 100 may operate to measure and/or estimate a volume of liquid. Inan exemplary embodiment, the first, second, and third planes 1300 a-care all parallel to each other, and each plane 1300 comprises amulti-operation electrode 140, wherein each plane 1300 a-c may operateas either the transmission electrode 110, the reception electrode 115,or a high impedance electrode.

The multi-operation electrodes 140 are operated in a sequence to obtaina more accurate measurement of the liquid. According to the presentembodiment, only one plane may operate as the reception electrode 115 atany given time, while the other plane(s) operate as either thetransmission electrode 110 or the high impedance electrode. For example,the first plane 1300 a may operate as the reception electrode 115 andthe second and third planes 1300 b-c may operate as the transmissionelectrodes 110 to measure a first liquid 1305. In a later sequence, thefirst plane 1300 a may operate as the transmission electrode 110, thesecond plane may operate as the reception electrode 115, and the thirdplane 1300 c may operate as the high impedance electrode. The capacitivesensor 100 may measure a second liquid 1310 in the same manner.

In the present embodiment, the sensing field 125 is formed between theplane operating as the reception electrode 115 and the plane operatingas the transmission electrode 110. The capacitance data obtained fromthe sequenced operation in conjunction with predetermined baselinecapacitance data regarding the measured object 120 may be utilized toobtain information about the object 120 and/or the volume of the liquid.

In an alternative embodiment, wherein the sensing element 105 is formedwithin sidewalls (planes) of the container 1400, the capacitive sensor100 may detect the level 1410 and/or volume of the material 1425 basedon the known dimensions of the container 1400, the dielectric constantof the material 1425, and the output voltage Vout. For example, if thecontainer 1400 is filled with water, the water will absorb part of thesensing field 125, and the capacitance of a full container of water willbe less than the capacitance of a half-full container of water. As such,the output voltage Vout will be greater for the full container comparedto the half-full container. The capacitive sensor 100 may compute thevolume of the material based on the output voltage Vout, length 1420,and width 1415 of the container, and the dielectric constant of thematerial 1425.

In various embodiments, the volume of a material, such as a liquid, maybe estimated based on predetermined output voltages. For example, a testcontainer containing a material with a known volume may be measured todetermine a baseline output voltage. When subsequent containers with thesame material are measured with capacitive sensor 100, the outputvoltage of the subsequent containers may be compared to the baselineoutput voltage to determine if the subsequent containers contain thesame volume of material as the test container.

The particular implementations shown and described are illustrative ofthe technology and its best mode and are not intended to otherwise limitthe scope of the present technology in any way. Indeed, for the sake ofbrevity, conventional manufacturing, connection, preparation, and otherfunctional aspects of the system may not be described in detail.Furthermore, the connecting lines shown in the various figures areintended to represent exemplary functional relationships and/or stepsbetween the various elements. Many alternative or additional functionalrelationships or physical connections may be present in a practicalsystem.

In the foregoing description, the technology has been described withreference to specific exemplary embodiments. Various modifications andchanges may be made, however, without departing from the scope of thepresent technology as set forth. The description and figures are to beregarded in an illustrative manner, rather than a restrictive one andall such modifications are intended to be included within the scope ofthe present technology. Accordingly, the scope of the technology shouldbe determined by the generic embodiments described and their legalequivalents rather than by merely the specific examples described above.For example, the steps recited in any method or process embodiment maybe executed in any appropriate order and are not limited to the explicitorder presented in the specific examples. Additionally, the componentsand/or elements recited in any system embodiment may be combined in avariety of permutations to produce substantially the same result as thepresent technology and are accordingly not limited to the specificconfiguration recited in the specific examples.

Benefits, other advantages and solutions to problems have been describedabove with regard to particular embodiments. Any benefit, advantage,solution to problems or any element that may cause any particularbenefit, advantage or solution to occur or to become more pronounced,however, is not to be construed as a critical, required or essentialfeature or component.

The terms “comprises”, “comprising”, or any variation thereof, areintended to reference a non-exclusive inclusion, such that a process,method, article, composition or apparatus that comprises a list ofelements does not include only those elements recited, but may alsoinclude other elements not expressly listed or inherent to such process,method, article, composition or apparatus. Other combinations and/ormodifications of the above-described structures, arrangements,applications, proportions, elements, materials or components used in thepractice of the present technology, in addition to those notspecifically recited, may be varied or otherwise particularly adapted tospecific environments, manufacturing specifications, design parametersor other operating requirements without departing from the generalprinciples of the same.

The present technology has been described above with reference to anexemplary embodiment. However, changes and modifications may be made tothe exemplary embodiment without departing from the scope of the presenttechnology. These and other changes or modifications are intended to beincluded within the scope of the present technology.

The invention claimed is:
 1. A capacitive proximity sensor, comprising:a sensing element, comprising: a plurality of multi-operationelectrodes; and a transmission electrode, wherein: the transmissionelectrode and the multi-operation electrodes form a sensing capacitor;and the plurality of multi-operation electrodes and the transmissionelectrode are coplanar along a surface of the sensing element whereinthe multi-operation electrodes are configured to operate as one of areception electrode and the transmission electrode; and a circuitelectrically coupled to the sensing element, wherein the circuitcomprises a switching device configured to selectively couple: one ofthe multi-operation electrodes to an amplifier; and each remainingmulti-operation electrode to one of the amplifier or a voltage source.2. The capacitive proximity sensor according to claim 1, wherein thetransmission electrode surrounds each multi-operation electrode.
 3. Thecapacitive proximity sensor according to claim 1, wherein the circuitfurther comprises a first external capacitor coupled in series with thesensing capacitor.
 4. The capacitive proximity sensor according to claim3, wherein the sensing element further comprises a reference capacitorcoupled in series with a second external capacitor.
 5. The capacitiveproximity sensor according to claim 4, wherein the circuit furthercomprises: a first variable capacitor coupled in parallel with the firstexternal capacitor; and a second variable capacitor coupled in parallelwith the second external capacitor.
 6. The capacitive proximity sensoraccording to claim 1, wherein the circuit further comprises adifferential amplifier coupled to the sensing element.
 7. The capacitiveproximity sensor according to claim 6, wherein the circuit furthercomprises: a first feedback capacitor electrically coupled between afirst input terminal and a first output terminal of the differentialamplifier; and a second feedback capacitor electrically coupled betweena second input terminal and a second output terminal of the differentialamplifier.
 8. The capacitive proximity sensor according to claim 1,wherein the multi-operation electrodes are aligned in one directionalong the surface of the sensing element.
 9. The capacitive proximitysensor according to claim 1, wherein the multi-operation electrodes arealigned vertically and horizontally along the surface of the sensingelement to form an array.
 10. A method for increasing the sensitivity ofa capacitive proximity sensor, comprising: forming an electric field ona surface having a plurality of coplanar electrodes, wherein: thecoplanar electrodes comprise a plurality of aligned multi-operationelectrodes; a transmission electrode is formed in the surface andsurrounding the multi-operation electrodes; and wherein the plurality ofcoplanar electrodes have a resting capacitance; establishing a referencecapacitance for the coplanar electrodes with a reference capacitor;selectively operating: one of the multi-operation electrodes as areception electrode; and the remaining multi-operation electrodes astransmission electrodes to increase a strength of the electric field.11. The method according to claim 10, further comprising sequentiallyoperating the multi-operation electrodes as the reception electrode inresponse to a movement of an object.
 12. The method according to claim10, further comprising adjusting the capacitance of a first and secondvariable capacitor formed within an integrated circuit based on a changein the resting capacitance of the plurality of coplanar electrodes andthe reference capacitance.
 13. The method according to claim 12, furthercomprising: forming a first equivalent capacitance by coupling a firstexternal capacitor in parallel with the first variable capacitor; andforming a second equivalent capacitance by coupling the second externalcapacitor in parallel with the second variable capacitor.
 14. The methodaccording to claim 10, wherein the multi-operation electrodes arealigned along the surface of the sensing element vertically andhorizontally to form an array.
 15. A proximity sensor system,comprising: a sensing element, comprising: a plurality ofmulti-operation electrodes; a transmission electrode, wherein thetransmission electrode and the multi-operation electrodes form a sensingcapacitor, and the plurality of multi-operation electrodes and thetransmission electrode are substantially coplanar along a first surfaceof the sensing element; a first reference capacitor; an integratedcircuit electrically coupled to the sensing element, wherein theintegrated circuit comprises a switching device configured toselectively couple: one of the multi-operation electrodes to anamplifier; and each remaining multi-operation electrode to one of theamplifier or a voltage source; a first variable capacitor coupled inseries with the sensing capacitor; a second variable capacitor coupledin series with the first reference capacitor; and a differentialamplifier; an analog-to-digital converter coupled to the differentialamplifier to convert an output signal of the differential amplifier to adigital value; and a central processing unit coupled to theanalog-to-digital converter, wherein the central processing unit isresponsive to the digital value.
 16. The proximity sensor systemaccording to claim 15, wherein the multi-operation electrodes areconfigured to be selectively operated as one of a reception electrodeand the transmission electrode according to a movement of an object. 17.The proximity sensor system according to claim 15, wherein the sensingelement further comprises: a first external capacitor coupled inparallel with the first variable capacitor; and a second externalcapacitor coupled in parallel with the second variable capacitor. 18.The proximity sensor system according to claim 15, wherein theintegrated circuit further comprises: a first feedback capacitorelectrically coupled between a first input terminal and a first outputterminal of the differential amplifier; and a second feedback capacitorelectrically coupled between a second input terminal and a second outputterminal of the differential amplifier.
 19. The proximity sensor systemaccording to claim 15, wherein the multi-operation electrodes arealigned in one direction along the first surface of the sensing element.20. The proximity sensor system according to claim 15, wherein themulti-operation electrodes are aligned vertically and horizontally toform an array.